Answer:
   
   The term 'gemara' means addition; The gemara is an addition to the
   Mishna. Interestingly, although there is only one Mishna, there are
   two gemaras, each developed by many rabbis over a few centuries. One
   gemara was developed in Israel, and is called the Yerushalmi; the
   other was developed in Babylonia, and is called the Bavli. You never
   find the gemara printed by itself. It is always printed along with the
   Mishna.
   
   When you have the Babylonian gemara and the Mishna printed together,
   it is called Talmud Bavli (The Babylonian Talmud).
   
   When you have the Israeli gemara and the Mishna printed together, it
   is called Talmud Yerushalmi (or the Jerusalem Talmud, or the
   Palestinian Talmud, or the Talmud of the Land of Israel.)
   
   Keep in mind that the gemaras do not stick closely to the text, but
   offer a huge amount of additional material which is only loosely
   connected to the Mishna. They supplement the Mishna with haggadic
   materials and biblical expositions, and are a source for history and
   legend.